1. Field of the Invention
The present invention relates to a light guide and a thin film keyboard with the light guide, more particularly to a light guide capable of enhancing brightness at parts thereof and to a thin film keyboard with the light guide.
2. Description of the Related Art
Referring to FIG. 1, a thin film keyboard 1 of a typical electronic device such as a cell phone generally includes a keyboard surface layer 11, a light guide 12 that is disposed under the keyboard surface layer 11, and one or more light-emitting components 13 (such as light-emitting diodes) which emit incident light that enters from one side of the light guide 12. The keyboard surface layer 11 is generally printed with numerals, letters, etc. As the light-emitting components 13 emit light into the light guide 12, the light guide 12 illuminates the keyboard surface layer 11 such that the numerals and symbols on the keyboard surface layer 11 appear more visible in a dim environment.
Nevertheless, due to the dimensions of the light guide 12 and the characteristics of light-emitting angle of the light-emitting components 13, as the light-emitting components 13 emit light into the light guide 12, bright zones 121 and secondary bright zones 122 less brighter than the bright zones 121 are formed in the light guide 12. As shown in FIG. 1, the secondary bright zones 122 are formed proximate to the two lateral sides of each of the light-emitting components 13 and proximate to the corners of the light guide 12 away from the light-emitting components 13. Moreover, if opaque ink is used in printing the keyboard surface layer 11, lower illumination brightness is provided to the numerals or symbols by the secondary bright zones 122.
Referring to FIGS. 2 and 4, current approaches to resolve the problem described hereinabove include printing 121 on a top face of a light guide 12 (illustrated in FIG. 2), forming V-shaped grooves 124 in a top face of a light guide 12 (illustrated in FIG. 3), and forming cylindrical holes 123 in a light guide 12 (illustrated in FIG. 4). Although these approaches attempt to refract a portion of incident light from the light-emitting components 13 in the light guide 12 toward and out of the secondary bright zones 122, the control of the locations toward which the refracted light is directed is compromised, and hence the increase in brightness is limited.